On Start9 it's pretty simple, if you are already running a LND node. Just install Alby Hub from the marketplace. Login with your Alby account, and away you go.
For a video tutorial, I highly recommend you check out the tutorial master himself, nostr:npub1rxysxnjkhrmqd3ey73dp9n5y5yvyzcs64acc9g0k2epcpwwyya4spvhnp8